The present invention relates to a thread cutting tap having an elongated body, comprising at a first end a connector portion adapted to be connected to a tool and at a second end a threaded portion for cutting out a thread in a wall of an opening into which said threaded portion is to be introduced, said threaded portion being provided with at least two cutting edges in the circumferential direction of said body, each of said cutting edges being an integral peripheral part of a flank portion extending substantially radially from the longitudinal extension of said body, said flank portions defining therebetween a chip removal flute in the longitudinal extension of said body for removal of chips cut from said wall, wherein at least one of said flank portions having a side-wall is provided with a chip-breaking member.
It also relates to a method of manufacturing such a thread cutting tap.
A thread cutting tap of this kind is known from Swenson U.S. Pat. No. 2,145,819. The therein described cutting tap has straight chip removal flutes. Such flutes are disadvantageous, since the transportation of chips is poor, risking to cause accumulation of chips in the flutes. It also suffers from the drawback that it can only be used at relatively low cutting speeds.
Other thread cutting taps are known from JP-A-61-136726 and JP-A-61-136725, according to which the chip-breaking member is an indentation of a surface of the flank portion. The chip-breaking member in the form of an indentation is however disadvantageous, because it is only applicable to straight flute taps, as machining of the flank portion for achieving the chip-breaking member is complicated. The document also only relates to thread cutting taps of larger diameters, as there must be space both for introduction of a lubricant and transportation of the chips through a central opening.
Another thread cutting tap provided with chip-breaking members is known from SU-A-1 039 661. The chip-breaking members described in that document are not arranged on a surface of the flank portions.